If my cat wore socks, his fur would change color. No, seriously. It really would. And I have the pictures to prove it. Okay, maybe not of him in socks. Because that’s just not going to happen. Ever. But I really could get his fur to change color. And anyone owned by a Siamese could do the same thing. It’s all thanks to a special gene they have in common: an albino gene. What? Wait. Siamese aren’t albinos. Actually, they are. Temperature-sensitive albinos.
When we think of an albino, we usually think of someone without pigment. But Siamese — and similar breeds — aren’t stark white, so what gives?
Siamese are temperature-sensitive albinos because of genetics
See, a cat’s coloring is determined by a set of eight different genes. They’re what tell a black cat to be black, or an orange cat to be orange. And then there are modifier genes — these can cause a cat’s fur to be patterned in a certain way, or mask the color altogether, like you’d see in the white bib-and-spats on your classic tuxedo kitty.
But Siamese and similar cat breeds have a special modifier gene called a Siamese allele that mutates the color gene. It inhibits pigment — in other words, it causes albinism.
But that modifier signal only gets through to a kitty’s fur if it’s above a certain temperature.
So, how does this gene work?
This modifier starts sending out its “stop the color!” message around 100.4-102.5 F (38-39.2 C), which is a cat’s standard body temperature. Anything lower than that and the mutation is blocked and the color gene can then do its color thing.
Because a cat’s body is cooler around his ears, paws, and tail, that’s where the color begins to kick in. In essence, these cats are walking heat maps. Kinda cool, huh?
Why are these cats born lighter and then darken as they age?
It’s pretty warm in the womb, so all kittens with this special modifier allele are white throughout gestation. They pop out as white kittens too, but once exposed to atmosphere, their extremities begin cooling.
Once they hit that critical temperature, those alleles that have been inhibiting the enzyme responsible for pigment turn off and color begins to develop — on the ears, paws, tail, and face.
Someone questioned why the face — that’s not an extremity. True, but we have a lot of holes in our faces: eyes, ears, nose, mouth (the same argument my dad used when I was a kid and wanted to pierce my ears: “You don’t need another hole in your head!”). All those cavities in the head account for enough of a drop in temperature to let the color kick in.
Notice this kitten’s nose is darkest? Big breathing holes there! And at this stage, his paws are just beginning to get their dark brown color.
So, let’s think about temperature-sensitive albinos for a sec
If all it takes to make these cats “go albino” on you is to increase their temp, what if you made a cat wear socks? Would his paws turn white?
First, good luck with that experiment. Be sure to let me know how that works out for ya, ‘K?
Seriously, if you could actually keep them on him, then, well, the answer is yes. Because coat color is lightened by high body temperatures and darkened by lower temperatures, a bandage covering the fur — or even cold weather — can alter the color.
One of my cats — a Tonkinese — had to have a four-inch swath shaved around his lower abdomen for a sonogram a few years back. It happened right before we entered one of the coldest winters on record. His fur grew back a shade darker. Fortunately, as spring turned into summer, his coat lightened once again.
But wait — the temperature-sensitive albino genes get even weirder…
There are actually two temperature-sensitive albino genes, and one of them is a bit more lazy than the other. The Siamese allele is the more efficient one, and cats carrying this have those pointed coat patterns we associate with the breed. The less efficient one was found in the Burmese cat, and therefore bears its name.
This makes total sense if you look at pictures of both breeds. Siamese have the most contrast whereas Burmese can sometimes have very little contrast. That’s why many Burmese — and some Tonkinese — aren’t described as pointed cats (such as seal point or blue point). They’re known as minks instead.
See how little contrast our guy has in the photo below? He’s considered a mink, not a point.
OK! Done with the hard science. Back to the cool stuff.
What if a Siamese cat didn’t have that modifier allele?
If you ignore the temperature-dependent albinism thing going on, genetically my Maxwell is a solid grey kitty.
And a sealpoint Siamese? Well, genetically that’s a black cat, only with alleles.
Interesting to think about, no?
Thumbnail: Photography ©studdio22comua | Thinkstock.
Read more about cats and science on Catster.com:
- What is a Cat Flehmen Response?
- What It Means to Be a Tabby Cat
- The Fascinating Facts Behind Cat Colors
Read more about Siamese cats on Catster.com:
- Who’s That Cat? The Siamese, if You Please
- Did You Know Siamese Cats’ Eyes Explain Why the Sky Is Blue?
- Silver Belle, a Senior Siamese Cat, Gets a Second Chance
- 1 Siamese are temperature-sensitive albinos because of genetics
- 2 So, how does this gene work?
- 3 Why are these cats born lighter and then darken as they age?
- 4 So, let’s think about temperature-sensitive albinos for a sec
- 5 But wait — the temperature-sensitive albino genes get even weirder…
- 6 What if a Siamese cat didn’t have that modifier allele?